title: The robust hydrogel hierarchically assembled from a pH sensitive peptide amphiphile based on silk fibroin.
abstract: Supramolecular polymers can be formed by self-assembly of designed subunits to yield highly ordered materials. In this paper, hierarchically structured materials, from molecules to nanofibers to macroscopical hydrogel, were fabricated by pH-induced assembly of C(12)-GAGAGAGY, a peptide amphiphile (PA) based on silk fibroin. Due to the different acid dissociation constants of the carboxyl and phenolic hydroxyl groups on tyrosine residue (Y), the PAs showed unique pH sensitive assembly and aggregation behaviors. It was found that not only the molecular-scale assemblies of these PAs gradually changed from cylindrical nanofibers to nanoribbons with the decreasing of pH value from 11 to 8 but also most of nanoribbons aggregated into parallel bundles in such a case. Further decrease of pH value resulted in a hierarchically structured robust and plastic hydrogel, of which the rheological moduli reached around 10(5) Pa. Moreover, noodle-like hydrogel fibers with bundles of nanoribbons aggregated parallel along the long axis in them could be steadily prepared under shear force. Taking the pH-sensitive reversible sol-gel transition, high modulus and plasticity into account, the hydrogel is believed to have significant potential applications in tissue engineering or as the biocompatible adhesives.
authors.affiliation: State Key Laboratory of Molecule Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Guo
authors.forename: Jinming
authors.initials: J
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jinrong
authors.initials: J
authors.lastname: Yao
authors.forename: Zhengzhong
authors.initials: Z
authors.lastname: Shao
mesh_terms: D000595:Amino Acid Sequence; D001672:Biocompatible Materials / Q000737:chemistry; D020285:Cryoelectron Microscopy; D005349:Fibroins / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D044367:Phase Transition; D053838:Scattering, Small Angle; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014014:Tissue Adhesives / Q000737:chemistry*; D014783:Viscosity; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D012996:Solutions; D013501:Surface-Active Agents; D014014:Tissue Adhesives; D005349:Fibroins